It's also very nice to know exactly which parts are in the computer. Most places selling a computer will list the sizes of your ram, hard drive, cpu, and video card. Most often they won't mention the exact components, so you don't know the quality of your parts.

It worries me that you don't really know how much you can do in the bios until you actually get the computer. What if the RAM or processor aren't quite setup right and you can't change it? What if it can't even properly support a component?